Abstract
Abstract. The study examines the observed storm-generated sea level variation due to deep depression (event 1: E1) in the Arabian Sea from 26 November to 1 December 2011 and a cyclonic storm "THANE" (event 2: E2) over the Bay of Bengal during 25–31 December 2011. The sea level and surface meteorological measurements collected during these extreme events exhibit strong synoptic disturbances leading to storm surges of up to 43 cm on the west coast and 29 cm on the east coast of India due to E1 and E2. E1 generated sea level oscillations at the measuring stations on the west coast (Ratnagiri, Verem and Karwar) and east coast (Mandapam and Tuticorin) of India with significant energy bands centred at periods of 92, 43 and 23 min. The storm surge is a well-defined peak with a half-amplitude width of 20, 28 and 26 h at Ratnagiri, Verem and Karwar, respectively. However, on the east coast, the sea level oscillations during Thane were similar to those during calm period except for more energy in bands centred at periods of ~ 100, 42 and 24 min at Gopalpur, Gangavaram and Kakinada, respectively. The residual sea levels from tide gauge stations in Arabian Sea have been identified as Kelvin-type surges propagating northwards at a speed of ~ 6.5 m s−1 with a surge peak of almost constant amplitude. Multi-linear regression analysis shows that the local surface meteorological data (daily mean wind and atmospheric pressure) is able to account for ~ 57 and ~ 69% of daily mean sea level variability along the east and west coasts of India. The remaining part of the variability observed in the sea level may be attributed to local coastal currents and remote forcing.
Highlights
Tropical cyclones (TCs) are the most destructive weather systems on the earth, producing intense winds, resulting in high surges, meteotsunamis, torrential rains, severe floods and usually causing damage to property and loss of life
We summarise the response of sea level of the two events in the Arabian Sea (AS) and the Bay of Bengal (BOB)
The highest surges usually occur to the right of the storm track at approximately the radius of maximum wind whereas Mandapam and Tuticorin were to the left of the track
Summary
Tropical cyclones (TCs) are the most destructive weather systems on the earth, producing intense winds, resulting in high surges, meteotsunamis, torrential rains, severe floods and usually causing damage to property and loss of life. In the northern Indian Ocean, both the Bay of Bengal (BOB) and the Arabian Sea (AS) are potential genesis regions for cyclonic storms. Intense winds associated with TCs, blowing over a large water surface, cause the sea surface to pile up on the coast and leads to sudden inundation and flooding of the vast coastal regions. Joseph et al (2011) examined the response of the coastal regions of eastern Arabian Sea (AS) and Kavaratti Island lagoon to the tropical cyclonic storm “Phyan”, during 9–12 November 2009 until its landfall at the northwest coast of India, based on in situ and satellite-derived measurements. Wang et al (2012) reported the variations in the oceanographic parameters due to the tropical Cyclone Gonu, which passed over a deep autonomous mooring system in the northern Arabian Sea and a shallow cabled mooring system in the Sea of Oman. Our interest is confined to a few minutes to days and analysis of the spectral features of sea level oscillations in the two basins
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